The present invention relates to space heating stoves, and particularly to improvements in such stoves for effecting efficient heat transfer from the stove into the space environs thereof. Although the present invention is described with specific reference to the preferred use of wood as the fuel for the stoves, it is apparent that the invention is not limited to the use of wood, and other fuels could be used in stoves embodying the features of the present invention.
Wood burning space heating stoves are generally well known, and their design is a highly developed art. These stoves utilize both radiation and convection modes for the transfer of heat to the environs. The radiation mode is effective in the immediate and close environs of the stove, but its effect diminishes rapidly with increased distance from the stove, and is practically nil in rooms separate from that in which the stove is located. On the other hand, the air convection mode establishes heated air currents that provide reasonably uniform heating over substantial distances from the stove, and if sufficiently efficient the heating can reach effectively into remote rooms. Therefore, it has been the object of the design of many space heating stoves to emphasize the convection mode of heat transfer.
In accordance with the present invention, the efficiency of the convection mode of heating is greatly enhanced. This is accomplished by providing a plurality of generally horizontal and laterally spaced flue ducts emerging from the stove, which are joined to a manifold at a point spaced a short distance from the stove, for conduction of the combustion gases to a stack or chimney. This structure provides a series of vertical channels defined by the spacing between the ducts and the spacing between the stove and the manifold, wherein the channels are surrounded by heated surfaces. This heat exchanger causes an organized flow of heated air to rise through these channels and to establish a significant organized convection air current. The efficiency of this heat exchange and organization of convection current is further enhanced by the positioning of elongate vertically oriented heat transfer fins within said channels.
For efficient use of wood burning space heating stoves, it is necessary to control the burning of the fuel. This is normally done by an adjustable or valved draft inlet. However, normally these stoves are provided with a single draft inlet and a single flue duct exiting from the fire box, which are normally both much smaller than the fire box and are centrally located with respect to the fire box. As a result, the flow of combustion air through the fire box is largely confined to a central area, resulting in non-uniform and inefficient burning of the fuel located to the sides of the fire box.
In accordance with the present invention, relative uniformity of burning of the fuel throughout the fire box is obtained, thereby improving the efficiency of the stove. This burning uniformity results from the use of the above-described plurality of flue ducts distributed across the top of the rear of the fire box, together with the provision of a plurality of controlled or valved draft inlets positioned across the bottom of the front of the fire box. In this manner, the flow of air is substantially uniform throughout the fire box. It is preferred that the number of draft inlets be the same as the number of flue ducts, and that they be located in corresponding alignment.
To illustrate the heating efficiency of a stove embodying the features of the present invention, a conventional six room (three bedroom) rambler, of approximately 1250 square feet, insulated in a normal manner as recommended for electric heating, was uniformly heated throughout at a temperature of 68.degree.-74.degree. F., over a one month period of 1194 degree days, with less than 0.6 cord of wood.
Another important aspect of space heating stoves is their aesthetic character. At the present time, these stoves are frequently used in conjunction with existing open fireplaces. It is preferred aesthetically that the stove be designed to be positioned in front of, and substantially to cover the fireplace opening, using the fireplace chimney for the stove flue. Accordingly, it is preferred that the stove be rectangular in shape. However, a rectangularly shaped fire box made of sheet steel tends to warp as a result of heating and cooling cycles.
In accordance with the present invention, however, warping is prevented by completing the formation of the six sided fire box while under two dimensional prestressing. After a five sided structure is completed--top, bottom, back and two sides--the front panel is applied. Initially, this six sided fire box is formed by spot or skip welding all seams. The two sides and the top and bottom are then stressed outwardly. While the box is retained in this stressed condition, the seams are fully welded to complete the box. The resultant built in stress eliminates any tendency of the box to warp.
It is therefore one object of the present invention to provide an efficient space heating stove.
Another object of the present invention is to provide such a stove having efficient convection heating characteristics.
Another object of the present invention is to provide such a stove having efficient fuel burning characteristics.
And still another object of the present invention is to provide such a stove of non-warping rectangular structure.
Other objects and numerous advantages of the present invention will become apparent to those skilled in the art, from a consideration of the exemplary and illustrative specific embodiment of the invention presented hereinafter.